Propeller nozzle

ABSTRACT

A propeller nozzle is provided in which the geometry of the nozzle profile varies. With such a propeller nozzle, the hull stream in the propeller zone can be changed to a field of a more rotationally symmetrical nature.

United States Patent 1 Jacobsen et a1.

[ June 12, 1973 PROPELLER NOZZLE [75] Inventors: Gunner Monrad Jacobsen, Skarer; Asbjorn Mollevik, Strommen, both of Norway [73] Assignee: A/S Strommen Straal Strommen-Rauioss, Strommen, Norway 22 Filed: June 3,1971 21 AppLNo; 149,740

[30] Foreign Application Priority Data June 11, 1970 Norway 2274 [52] 11.5. CI. 115/42 [51] Int. Cl B631! 1/14 [58] Field of Search 115/42; 239/601;

[56] References Cited UNITED STATES PATENTS 3,455,268 7/1969 Gordon 115/42 Primary Examiner-Richard E. Aegerter Att0rney1-1olman & Stern [57] ABSTRACT A propeller nozzle is provided in which the geometry of the nozzle profile varies. With such a propeller nozzle, the hull stream in the propeller zone can be changed to a field of a more ratationally symmetrical nature.

2 Claims, 5 Drawing Figures PROPELLER NOZZLE BACKGROUND OF THE INVENTION This invention relates to means for improving propulsion effeciency and more particularly to improve propeller nozzles.

Propulsion devices for ships with propellers utilizing nozzles which enclose the propellers are known. It is further known to shape and arrange the propeller nozzle in such relationship to the propeller that the propeller will come to operate at the place where the propeller nozzle has its smallest flow cross section, and has a quite small clearance with the propeller blade circle. Furthermore, the propeller nozzle is so shaped that the flow section behind the propeller changes very slightly or not at all, while the fiow section in front of the propeller increases in the forward direction. It is also known to shape the propeller nozzle inlet edge rounded with a large radius.

The purpose of using propeller nozzles is to improve the propulsion efficiency. As a rule, propeller nozzles have been rotationally symmetrical, and have been designed according to mean values for the hull stream. The hull stream in the propeller zone is, however, especially for ships with greater block ratio or block coefficient, as is the case with most larger tank/bulk ships, not rotationally symmetrical.

SUMMARY OF THE INVENTION The invention has its basis in the recognition of this, and according to the invention a propeller nozzle is suggested in which the geometry of the nozzle profile varies. With such a propeller nozzle, one can change the hull stream in the propeller zone to a field of a more rotationally symmetrical nature, such that each propeller blade sees a more even hull stream picture during the rotation of the propeller.

According to the invention, the propeller nozzle is built from nozzle sectors with unequal profiles, such that the propeller nozzle has profiles varying discontinuously. The transitions from one profile type to another are so made that turbulence preferably is not created. A design of this type offers productional advantages.

The geometry of the propeller nozzle does, furthermore, depend on the profiles one wishes to employ. It is, in this way, possible to make a significant part of the propeller nozzle rotationally symmetrical while the variations in the profile are to be found in the forward edge of the propeller nozzle. The propeller nozzle may be so designed that the inside of the propeller nozzle behind the propeller zone is made to be common for all the profiles.

The profiles may vary both in size, shape and type. In order to increase the propulsion efficiency still further, the propeller nozzle may, according to the invention, be provided with so-called high-lift slits in front of the propeller zone. High-lift slits are here inclusive of any opening through the profile. By utilizing high-lift profiles for the propeller nozzle, one may obtain a more uniform nozzle effect around the propeller nozzle. The utilization of the high-lift profiles may give a reduced propeller nozzle length with an equal nozzle thrust. The nominal opening angle of this profile, may also be increased -30 percent, approximately, over the values valid for ordinary profiles.

A significant advantage of using a high-lift profile is that it facilitates an increase in the thickness of the boundary layer on the inside of the propeller nozzle in the path of the propeller blade tip. This reduces the demands of small clearances for the propeller blade tips.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be further explained with reference to the drawings, in which FIG. 1 in a front view of a propeller nozzle according to the invention.

FIG. 2 is a side view of the propeller nozzle shown in FIG. 1.

FIG. 3 is a fragmentary front view of another propeller nozzle according to the invention.

FIG. 4 is a view illustrating a part of the propeller nozzle in FIG. 3 folded out flat.

FIG. 5 in a view in partial section through a propeller nozzle according to the invention, with a high-lift profile.

DETAILED DESCRIPTION OF THE INVENTION In FIGS. 1 and 2 are shown a propeller nozzle in which the body thereof is provided with an upper nozzle sector 1, within which the profile is uniform over the whole sector, a lower nozzle sector 2, which, also has an uniform profile on the whole sector and a side sector 3, with a mirror image sector 4. Also in the two side sectors, the profile is uniform within the sectors. The profiles in the nozzle sectors 1 4 are, however, individually different, with exception of the two side sectors 3, 4, as is evident from FIG. 2.

In FIG. 2, an indication of the rounding off of the profile is, further, drawn by dotted lines 5, 6.

Another propeller nozzle according to the invention is shown in FIGS. 3 and 4. In FIG. 3, only one half of the propeller nozzle is shown, in that the other half is symmetrical about the vertical center line. As shown in FIG. 3, the nozzle has several nozzle sectors 7, 8, 9 and 10 which have mutually different profiles, respectively, as is evident from a closer study of FIG. 4, in which the propeller nozzle in FIG. 3 is shown unfolded. FIG. 4 shows clearly that the nozzle sector 7 has a certain profile 11, while the nozzle sector 9 has a second profile 12 and the nozzle sector 10 has a third profile 13. In FIG. 4, the dotted lines 14 and 15 indicate transitions between sectors, in order to avoid turbulence. The propeller zone is indicated by the dotted line 16. Behind the propeller zone, the inside 19 of the propeller nozzle is common for all of the profiles.

By means of the propeller nozzle types shown, one may obtain an alteration of the hull stream in the propeller zone to a field of a more rotationally symmetrical nature, with an increase in the propulsion efficiency as a result of this alteration.

FIG. 5 shows a partial section through a profile, which may be a profile in one of the propeller nozzles shown in FIGS. 1 4. Profile 21 is equipped with high lift slits 18. The leading part of the profile is connected by means of webs 19 to the main part of the profile. The high-lift slits 18 are, as is evident from FIG. 5, arranged in front of the propeller zone. In FIG. 5, a propeller blade is indicated by 20.

In FIGS. 1 and 2, two dotted lines are drawn near theprofile 4. These dotted lines indicate two other possible variations in the profile. Generally, the profiles may be varied according to the specific situation, in order to obtain the most favorable solution.

Having described our invention, we claim:

1. A nozzle for a propeller for improving propulsion 2. The propeller nozzle as claimed in claim 1 in which efficiency, comprising a body provided with a varying the body has-a propeller zone, and the inside of the profile, the improvement being that the body includes body behind the propeller zone is common for all the sectors, each sector having a constant profile and a profiles. stepwise transition between the sectors. 5 

1. A nozzle for a propeller for improving propulsion efficiency, comprising a body provided with a varying profile, the improvement being that the body includes sectors, each sector having a constant profile and a stepwise transition between the sectors.
 2. The propeller nozzle as claimed in claim 1 in which the body has a propeller zone, and the inside of the body behind the propeller zone is common for all the profiles. 